Conventionally, studies have been made on synthesis of condensation products by hydrolysis and condensation reaction, with use of a sol-gel method in which a silane compound having a hydrolyzable silyl group is used as a material. Such condensation products are to be used in hard coating agents for plastic materials and ceramic materials, protective films for liquid crystal display elements, semiconductor electric insulation materials, curing agents for coating materials, and the like.
For example, Patent Literature 1 discloses a method for producing an alkoxysilane condensation product in the presence of an acid catalyst. In this method, tetrafunctional alkoxysilane such as tetraethoxysilane is used as a material. Meanwhile, Patent Literature 2 discloses a production method for hydrolyzing/condensing (i.e., hydrolyzing and condensing) trifunctional organic alkoxysilane such as vinyl trimethoxysilane in the presence of a base catalyst.
As described above, according to a general sol-gel method, hydrolysis and condensation are accelerated by use of an acid catalyst or a base catalyst. However, since acids and bases are often caustic substances, technical consideration is essential in regard to corrosion of a reactor material or a storage equipment material. Further, in many cases, removal or neutralization of an acid or a base after synthesis is required in practice. It is however not easy to completely remove an acid or a base. Further, in a case where neutralization is carried out, a process is complicated and impurities increase (see Patent Literature 3).
Further, when an acid catalyst or a base catalyst is used in hydrolysis and condensation of a silane compound containing a highly active organic functional group such as an epoxy group, an organic functional group is destroyed and consequently deactivated.
Patent Literature 4 reports a technique according to which a fluoride salt as a neutral compound is used as a catalyst. The term “neutral” in Patent Literature 4 does not mean that an aqueous solution of a fluoride salt itself exhibits neutrality in terms of pH, but merely means that in a case where a fluoride salt is dissolved in water, a counter ion of a fluoride ion is not a hydrogen ion. In fact, many aqueous solutions of a fluoride salt exhibit weak acidity. Further, many fluoride salts are known to produce a highly toxic hydrofluoric acid in an acid aqueous solution. Further, a concern exists in that silanol produced in reaction may promote generation of hydrofluoric acid.